Why is WinZip slow when extracting some files?

The Windows Attachment Manager service can slow the WinZip extraction process significantly.

When you download files from a web page or receive file attachments in your email, Windows creates an alternate NTFS data stream for the file in most cases. This data stream contains Internet Zone information. The information is used by the Attachment Manager to determine how the file should be handled (e.g., whether it should be blocked altogether, or allowed to be opened with warnings, etc.)

Zip files are not considered to be high risk by Windows, by default. Zip files themselves, then, are not blocked. However, as they can serve as a vehicle for files that are considered high risk and, because WinZip is Attachment Manager aware, it honors the presence of the alternate data stream in the Zip file, if it exists. WinZip passes this information on to Windows for files you attempt to extract. This means that with downloaded/received Zip files, all files you attempt to extract are subjected to additional processing by the operating system, and that files not blocked by Windows, extract with the same Zone information as the Zip file.

To prevent slow extraction:

Right click the Zip file

Choose Properties

Click Unblock

Click OK to close Properties

This will remove the zone information and eliminate the Attachment Manager's involvement in the extract process.